Brake master cylinders having a contactless detection means are known in principle.
For example, DE 10 2004 014 808 A1, which is incorporated by reference, describes a brake master cylinder, a magnet being provided as transmitter element such that it is arranged between two pistons in a bore of the housing and can be displaced relative to at least one of the pistons by means of spring means. In order to guide the magnet, a piston has a journal-like piston section, on which a carrier for the magnet is arranged in a resiliently prestressed manner. However, an arrangement of this type of a magnet requires a relatively complicated construction with additional components and conflicts with a regular desire for a reduction of the dimensions.